import java.util.Scanner;
public class Fibonacci {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int ret = Fi(n)-Fi(n-1);
        System.out.println(ret);
        }
    public static int Fi(int n) {
    if (n<=1)
        return 1;
    else
        return Fi(n-1)+Fi(n-2);
    }
}
